Maybe
Perhaps you should set your computer filters to keep those sites from being accessed. After you have worked through this you could slowly lift the restrictions. I don't believe in prying too hard into my childs life but we have talked about this and I occasionally check the history of his computer but I will not purchase software to spy on him and I don't check his myspace page. Part of parenting is allowing a child choices. I think a moderate approach is more effective at building trust. His admission to you is a good first step and I think you are taking the right path but you should be honest with you children. They are smarter than we give them credit for. And It is possible to accidentally go to a site that would make the account holder criminally liable.